When should infrastructure assets be renewed?: the economic impact of cumulative tonnes on railway infrastructure

This paper provides empirical evidence on the optimal timing of rail infrastructure renewal. Using an econometric approach on data from the Swedish railway network, we establish a relationship between cumulative tonnes and maintenance costs, as well as between cumulative tonnes and infrastructure failures that cause train delays. Together with average values on delay hours per failure and assumptions on passengers per train, we perform example calculations on the optimal timing for a track renewal. This timing will depend on the case considered, such as whether traffic intensity is high or low. Empirical evidence on the relationship between line capacity utilisation and delay time can provide more robust estimates for the different cases considered by an infrastructure manager. Still, the results in this paper is a significant step towards a usable cost-benefit analysis model for the timing of rail infrastructure renewals.